Repairs

After serving me for many years, my good old keyer, microham mkII stopped keying last night.
Of course this happens at the least convenient time, during a contest.
I got an idea of where the fault lies, but if any of you guys has a schematic if the MKII lying around, I would VY much like a copy.
73 de LA6TPA
Geir

Earlier I fried my elevation motor, and I was in need of a quick fix.
The plan is to eventually rewind the original 24VAC motor but this will take some time and materials I do not have for the time being.

The quick, non-destructive solution was to get a $7 worth 24VDC motor, and put that in to service.
All I had to do, besides the rectifier system, was to drill two new holes in the motor bracket and move the cogwheel over to the DC motor shaft.

The ZHENGKE ZGA25RP DC 24V 500RPM Micro Gear Box Motor have an unload speed at about 500 rpm, so the elevation is moving at about 1/5 of the original speed. However, this is more than sufficient when tracking the moon. The stall torque is also sufficient due to the low gearing.

I am considering to get a larger, faster and more powerful DC motor, but then I will have to ether do a non-reversal cogwheel modification or get hold of an another cogwheel that will fit.

Left: Original 24VAC motor.Right: very small 24VDC motor fixed to the original bracket .

After the antenna work I did in my previous post, my GPSDO MKII had stopped working.
Reason was that I had been a little too rough with the small coax going to the rooftop GPS antenna.
The coax had shorted and this being an active antenna the RF-choke on the Jupiter GPS board feeding the antenna with 5VDC was fried. Having no idea on what value the original inductor has I had to substitute it with something, I chose a 33nH inductor with a self-resonate frequency around 1.7GHz.

Last night I got a Foscam FI9821W ip-cam to play with, but within an hour it was broken because the firmware upgrade failed. I was simply trying to upgrade from 1.1.1.12 to the 1.1.1.13 version. The camera interface reported that the update was successful but the camera never came online again. It does its servo calibration routine when powered but that is all. Searching the internet I can see that there are several reports of this problem but as far I can see no cure other than asking the supplier for a RMA. I am not interested in sending this cheap device half around the world for a repair or exchange unit, so I decided to try to fix it myself. Luckily, I was able to get it going again and the process was fairly simple.

Warning: This process worked for my problem but I cannot guarantee that it will work for you.

Then launch your terminal program with these settings. Of course you will have to find your own com port number.

If you have done it right you shold get text flying over your screen when powering the camera.This text will after a little while halt.With your wired network connected to the camera execute the following commands:

First press enter or esc to get to the promt.type: “/etc/init.d/S80network” + entertype: “ifconfig eth0 192.168.1.2 netmask 255.255.255.0 broadcast 192.168.1.255” + enter (you will have to adjust the ip address so it fits in your network)

Now the camera web server should be accessible from your browser again. Point it to http://your ip address above:88 (in my case http://192.168.1.2:88) Camera will not work and lot of info will be missing because many processes are not running, never mind this. Then go to the system – firmware upgrade page and upload 1.1.1.12 version firmware. When camera is done with the upload and reboot it should be working again.

After this downgrade, I was successful in upgrading to version 1.1.1.13. I have several times tried to downgrade and thereafter upgrade but I have not been successful in reproducing the error.

I’ve got these cheap but good working wireless headphones branded Welltech 40699/FKH51a. After several years of use the two AAA NiMH Rechargeable Batteries dies and I replace them with new ones. But hey, they will not recharge, what is wrong? Having a closer look at the headphones I discover that the battery cases have a protective device to prevent non-rechargeable batteries getting charged. This device is a simple contact spring that has to be grounded to the battery minus potential to enable recharging. So the solution was to remove some of the insulation material at the bottom of the batteries, and now the headphones again are recharging the batteries.

I have also done a small modification to the base unit. I have removed the small internal wire antenna and fed the signal to an external sma connector. This enables use of a better antenna which improves coverage when moving around. A simple antenna for the 850 or 900 Mhz GSM bands works good for this unit which operates on the 860 Mhz LPD band.